Containers for aerosol formulations commonly comprise a vial body coupled to a valve. The valve comprises a valve stem through which the formulation is dispensed. Generally the valve includes a rubber valve seal intended to allow reciprocal movement of the valve stem while preventing leakage of propellant from the container.
It has been found that in some conventional devices the valve stem tends to drag during the actuation cycle with the result that the user may perceive a ‘notchiness’ as the valve stem is depressed and released. This may be partly caused by the drug sedimenting or precipitating out of the drug-propellant suspension or solution formulation and depositing on the internal valve components, the presence of drug on the sliding interface creating increased friction during operation.
The Applicants have now found that the above described problem of notchiness may be ameliorated without compromising sealing performance if the valve seal has a wiper component in addition to a sealing portion. The wiper acts on the valve stem to prevent the deposit and accumulation of drug particles and propellant at the point of contact between the sealing portion and the valve stem. The ‘notchiness’ that can increase with repeated actuations of the aerosol container is therefore reduced.
Any ‘notchiness’ may be further reduced by shaping the seal so as to reduce the area of contact between the seal and the valve stem. This results in reduced deformation of the seal and a reduction in the friction at the contact point with the valve stem.